DEGRADATION OF LOW-MOLECULAR-WEIGHT FRAGMENTS OF PECTIN AND ALGINATESBY GAMMA-IRRADIATION

Low molecular weight (LMw) fragments of polygalacturonic acid (PGA) ob tained by enzymatic degradation, as well as low molecular weight fragm ents of pectin (methyl esterified polygalacturonic acid) and alginates obtained by mechanolysis have been used to study the mechanism of rad iation-induced degradation. By means of high performance anion-exchang e chromatography (HPAEC), the degradation of specific entities induced by gamma-irradiation and the formation of new compounds were monitore d. The LMw fragments of PGA, pectin and alginates showed an increasing reduction in the degree of polymerisation upon exposure to increasing irradiation doses. An alginate with a high mannuronic to guluronic ac id ratio appeared to be more sensitive towards irradiation than an alg inate having a low ratio. Degradation of the PGA fragments by irradiat ion can be ascribed to hydrolytic cleavage of glycosydic bonds, althou gh HPAEC analysis revealed that also other, unknown products were rele ased during the irradiation process. Storage of various irradiated PGA fractions at -20 degrees C did not affect significantly their average molecular weight and had no effect on their HPAEC elution pattern.